public function defineParameter($key, $type, $label, $default = null)
{
if (isset($this->parameter[$key])) {
throw new \InvalidArgumentException('Parameter already define in bag: ' . $key);
}
$parameter = new Parameter();
$parameter->setKey($key);
$parameter->setType($type);
$parameter->setLabel($label);
$parameter->setDefault($default);
$this->parameter[$key] = $parameter;
}